1. Field of the Invention.
The present invention relates to an abrasive composition, and in particular to an abrasive composition used in chemical-mechanical polishing for a semiconductor surface in a semiconductor manufacturing process.
2. Description of the Related Art.
Recently, semiconductor devices have been improved very rapidly in their level of integration and structural fineness. To obtain high resolution in a photolithography process, demagnification optical exposure is employed in the main stream of the art, its resolution limit r and depth of focus DOF being shown in the following equations (1) and (2). EQU r=k.sub.1 -.lambda./NA (1) EQU DOF=K.sub.2 .multidot..lambda./NA.sup.2 ( 2)
As seen from the equations, when an optical system having a larger numerical aperture NA is used to increase a resolution limit r, depth of focus DOC becomes decreased, thus lowering the focus margin of the process.
On the other hand, structures of semiconductor devices became more complicated, accompanying advancement of multilayered wiring techniques. When wiring is multilayered, irregularity is increased more in a pattern in an upper layer of a semiconductor device, and/or defect such as disconnection of the wire is liable to occur because of deficiency of step coverage. Further, an optical system with large NA has difficulty in forming an entire image of a pattern.
Accordingly, planarization of inter layer insulating film has been studied, and in particular, chemical-mechanical polishing (CMP) has been noted because it can planarize wider areas and is researched vigorously.
In conventional chemical-mechanical polishing, planarization polishing of inter layer insulating film is performed with an abrasive composition consisting of silica dispersed in water, and employing an apparatus such as shown in FIG. 6. In FIG. 6, 601 refers to a wafer, which is mounted on a wafer support 602 which turns on its axis, revolves, and swings left, right, back and forth, with the wafer's surface to be polished being directed downward. A reference number 603 refers to an abrasive composition supply pipe for dropping an abrasive composition. By 604, is referred to a polishing pad mounted on a rotating pad support 605.
The abrasive composition is dropped onto the polishing pad 604 through the supply pipe 603. Relative movement between the wafer 601 and the pad 604 makes the dropped abrasive composition enter between the wafer 601 and the pad 604, thus the inter layer insulating film of the wafer 601 is polished by sliding on and being rubbed by the pad 604.
According to this conventional polishing method, however, it is difficult to supply the abrasive on a wafer surface entirely and uniformly, and its polishing uniformity is poor.
As a method to solve the problem, there has been studied a method in which holes are provided in a polishing pad and an abrasive composition is supplied through those holes, which increased uniformity in supplying an abrasive composition onto a wafer surface. However, the obtained uniformity in polishing is not sufficient, and its reproducibility is poor.
The present inventor has studied the cause of low polishing uniformity from both the viewpoint of polishing methods and abrasive compositions, to find that polishing uniformity is greatly affected by composition of an abrasive composition and static electrification properties of a polishing pad and the abrasive composition. The present invention has been completed, based on those findings.